Why are the lanthanides and actinides placed below the periodic table?
Partly for convenience, since a "super-wide" form periodic table would be too wide to fit on a single normal page. This is also justified chemically, because all of these elements have chemical properties very similar to each other and to other elements in column 3.
The lanthanides are in period 6, the actinides in the 7th period. Periods are numbered vertically (down from the top) but run across the periodic table in rows. The columns, sometimes called "groups", are numbered horizontally from left to right but actually run from top to bottom. The lanthanides and actinides are all in column 3, but, because they take up so much room in the periodic table, are placed below it.,
You can find periodic tables where the lanthanides and actinides are drawn in the sixth and seventh period. This is actually where they belong on the periodic table. But drawing them there makes the table unmanageably wide. Placing them at the bottom and drawing arrows where they go keeps the table at a usable width. In the related links below, there is a link to an online periodic table that lets you see the lanthanides…
In most wide form periodic tables, the lanthanides are in a row below the normal part of the table, with a reference showing that all the lanthanides correspond to period 6 column 3. Sometimes the lanthanide element with the lowest atomic number, lanthanum itself, is shown in the main table and the other lanthanides in a row below the main table.
In 1869 the Russian chemistry professor Dmitri Ivanovich Mendeleev and four months later the German Julius Lothar Meyer independently developed the first periodic table, arranging the elements by mass. its invention though is generally credited to Russian chemist Dmitri Mendeleev . The layout of the table has been refined and extended over time, as new elements have been discovered. In the 1940s Glenn T. Seaborg identified the transuranic lanthanides and the actinides, which may be…
In group 6, the largest radius would be for the element promethium (element 61) which is one of the two unstable elements below Lead. In the columns (groups), the largest atomic nucleus will usually be in the lowest period (row) because it will have the most electron shells. However, the lanthanides in period 6 (elements 57 to 71) have larger radii than the actinides in period 7 (elements 89 to 103).
One day you discover element 126 what effect will this discovery have on the shape of the periodic table we currently use?
This is only a matter of print layout of the table, it would double the number of columns (36!) when placed in between group (column) 3 to 4 in period 6: 57La to 72Hf and in between group (column) 3 to 4 in period 7: 89Ac to 104Unq. But they are still placed IN the periodic table, though not printed in.
Magnesium is a metal because it displays the properties of metals. These properties are displayed below: 1.) Magnesium is shiny. 2.) Magnesium is malleable and ductile. 3.) Magnesium has a relatively high melting/boiling point. 4.) Magnesium is hard. Furthermore, magnesium is placed in group II which is towards the left side of the periodic table. Elements placed towards the left side of the periodic table are metals. The metallic properties of elements decreases from left…